DEV: Switch to use pnpm (#57)

Author: tyb-talks

.npmrc

@@ -0,0 +1,2 @@
+engine-strict = true
+auto-install-peers = false

package.json

@@ -5,5 +5,11 @@
     "ember-template-lint": "6.0.0",
     "eslint": "8.57.0",
     "prettier": "2.8.8"
+  },
+  "engines": {
+    "node": ">= 18",
+    "npm": "please-use-pnpm",
+    "yarn": "please-use-pnpm",
+    "pnpm": ">= 9"
   }
 }